Delivery of a carbureted mixture into the combustion chamber may be achieved through parts driven by a reciprocating motion, such as valves. A system of this type is proposed in patent application EN-89/17,484.
However, engine performances may be limited by valve injection systems, notably concerning control of the beginning and of the end of the injection process and the opening area for the carbureted air (oscillation problems).
Moreover, these systems have to be mounted in cylinder heads of relatively large size. One improvement consists in using rotary throttle valves for the control and delivery of a carbureted mixture.
Thus, patent application EN-90/06,323 provides the use of rotary throttle valves for controlling the pneumatic injection of fuel into a two-stroke engine.
The throttle valves disclosed have a rotational axis located in a plane perpendicular to the axis of the cylinder. Throttle valves are pierced with a transverse channel for communicating the linking channel with the combustion chamber and they are connected to driving means for rotating them as a function of the rotational speed of the engine crankshaft.
In comparison with valves, such throttle valves may be run at a higher speed and allow a higher flexibility in the injection adjustment.
However, sealing problems remain, notably at the throttle valve inlet.
Sealing devices are sometimes provided to that end, either upstream or downstream from each throttle valve, or in both places.
Patent application FR-2,559,208 relates to a throttle valve for controlling the exhaust and/or the intake of gas from and/or towards a combustion chamber, and on which one or several sealing parts are applied. The improvement envisaged in this patent consists of a lubrication and a refrigeration of the contact surface between the sealing part(s) and the throttle valve.
The sophistication of this system does not ensure perfect reliability, notably concerning sealing.